The present invention relates to a radio system of the type including a radio broadcasting device disposed in a motor vehicle for establishing two-way radio communication between a mobile radio transmitting and receiving station and a stationary radio transmitting and receiving station.
It is known to effect radio comunications between mobile radio stations via a stationary radio relay station, as described, for example, by Werner Giese in the text Funksprechen [Radio Voice Communication], published by Berliner Union, Stuttgart, 1971, at pages 65 and 66. In this case either the simplex or duplex mode is employed. In the prior art it was not possible, however, to communicate directly or via a radio relay station between a hand-held two-way communications device which operates, for example, in the 2 m-band and a radio station which operates in another frequency range, for example the 4 m-band.